Haptic and Thermal Rendering of Astronomical Data: A Multimodal Approach to Inclusive Science Communication

Abstract

Universal Accessibility in Astronomy requires a paradigm shift from visual-centric communication to multisensory data interaction. Because astronomy communication relies inherently on high-resolution imagery and visual metaphors, it creates significant accessibility barriers for blind and low-vision (BLV) audiences. To address this, multimodal encoding offers a feasible and meaningful solution by redistributing information across alternative sensory channels, ensuring that the absence of sight does not preclude the comprehension of spatial data. This article explores the development and evaluation of a low-cost, multimodal tool designed to represent complex astronomical concepts—specifically stellar magnitude and color—through tactile and auditory stimuli. Unlike traditional methods, our approach focuses on the haptic-cognitive link, allowing users to “feel” data through physical relief models. We present a structured impact study involving a heterogeneous group of blind, low-vision, and sighted participants. The methodology followed a mixed-methods approach, including a participatory workshop with 20 individuals and a detailed usability assessment with a core group (n= 6) of blind and low-vision participants. Preliminary results from this pilot phase demonstrate that multimodal integration effectively reduces the perceived mental effort for complex spatial data comprehension. Quantitative and qualitative feedback suggests that tactile-auditory sensory substitution not only improves accessibility but also enhances engagement and information retention across all user groups. These findings highlight the potential of multimodal models in transforming public scientific environments, such as museums and observatories, into inclusive, interactive spaces.

1. Introduction

The landscape of science outreach is undergoing a significant transformation. Far from being a peripheral activity, the ‘translation’ of complex research for general audiences is now a key site of innovation. Success in this field relies on specialized teams that bridge disciplines to create inclusive, impactful experiences for the public.

There are certain foundations on which commitments to the community are based when it comes to outreach activity, such as trust, competence and warmth or empathy in dealing with people; these characteristics are not stable, they are not seen in all cases as necessary when communicating science with the public and therefore, the execution of many programs in this area is ineffective, in the sense of reducing the gap between scientists and non-scientists [1]. When discussing Inclusive Science Outreach, the proposal of "universality" in content production entails creating resources for everyone, fostering community engagement, and prioritizing educational efforts and professional development as the foundation of the activity.

The dissemination of science involves sharing knowledge, discoveries, and technological advancements with the general public, including non-scientists. One of the ways to reach diverse audiences is through science exhibitions, museums, and, in recent years, thanks to science and technology exhibitions in large spaces, interactive installations and performances, allowing public participation in the approach to knowledge. On the other hand, there is currently greater awareness of the need for a multisensory approach to science education through tools that allow multimodal access to knowledge. Accessibility involves the development of resources specifically designed to accommodate various disabilities—such as blindness, deafness, and attention deficit disorders—while also offering value to non-disabled persons.

Inclusive education in the field of astronomy focused on accessibility, through a multidisciplinary approach that brings space closer to Earth using specialized resources and tools [2], with preeminence in tactile models of the celestial objects such as stars, galaxies and nebulas.

In recent years specific tactile models are being proposed: for galaxies [3]; for stars [4]; for Eta Carinae Homunculus [5]; and statistical studies, analysing the impact of the models [6], support the idea of the positive reception of these tools by different audiences. The use of innovative softwares to produce detailed 3D representations of complex images, as the Cosmic Microwave Background [7], the sonification of data [8], models that proposes the use of the sense of taste to explore the content of the universe as the G-Astronomy project (Trotta, R.: The Kitchen Theory [9]), or a multisensory approach [10], enriched the ways to show astronomy for all. This multisensory strategy fosters the development of diverse skills in individuals of all abilities.

To assess the impact and satisfaction of users engaging with multimodal outreach materials, it is essential to establish control or focus groups that enable evaluation of the proposal’s benefits and effectiveness. However, conducting such studies in restricted settings or with small sample sizes poses significant challenges. For this reason, the project was designed from the outset for implementation in a broad public context, targeting diverse audiences and enabling effectiveness monitoring without prior bias.

This context was provided by special science exhibition as Tecnópolis [11], initially in its Buenos Aires editions from 2011 to 2016, and later through its traveling exhibitions, which offered unprecedented opportunities for large-scale visitor feedback. Beyond Tecnópolis, other initiatives have also contributed, such as citizen science projects like ReInForce [12]. These proposals and projects, incorporated tactile materials and sonification techniques, as the sonoUno software [13,14,15,16] to further spark public interest in science, in a multimodal framework.

This article describes the design, evaluation and exploitation of a “thermal constellation”, in which the colors of the stars are in connection with the temperatures, beyond the initial models in which only the magnitude issue was considered. The goal of this work is not to achieve population-wide final general acceptance or a generalization in the results, but to demonstrate that the thermal-tactile mapping of astronomical data is physically perceptible and cognitively intuitive for the end-user.

While this research follows a proof-of-concept framework—consequently limiting its initial findings to preliminary tests with users of diverse backgrounds—the study focuses on a restricted group of volunteers (as detailed in the following sections). Nevertheless, the scalability of this multimodal model and its potential future applications remain highly promising.

2. Multimodality in Astronomy

Astronomy for Inclusion is often associated with the development and adaptation of tools and resources for people with visual impairments. However, this work moves beyond that partial approach. We advocate for a multimodal (multisensory) approach [17,18,19].

Furthermore, the sense of vision encompasses a broad spectrum, ranging from standard vision to total blindness. Individuals with low vision may face challenges such as difficulty perceiving shapes, colors, contrasts, distances, or textures, as well as issues with light-to-dark adaptation. Others may experience a reduced visual field or diminished night vision [20]. These characteristics may be congenital or acquired with age; therefore, inclusion in the sciences must also encompass the needs of the elderly population.

Blind or visually impaired people shift their environmental interaction towards auditory (which may also be affected in elderly persons), olfactory/taste, and tactile information, relying on more complex mental spatial representations to locate objects [20]. The loss of vision does not immediately translate into an improvement in other senses, because the cognitive domain is part of the communication between the brain and the world [21], and a set of abilities needs to be trained. Among people with visual impairments, the tactile sense tends to become more refined through continuous and purposeful use. However, this enhanced perceptual capacity often remains unrecognized until specific situations demand its application, for instance, in the detection of temperature variations, the experience of physical injury, or interaction with textured surfaces. Many times sight is not enough for the mental images of some object, and we need to complement the vision of it with touch (for example, feeling the texture of a fabric or the surface of a table or wall, or recognizing the shape of a body, or detecting the temperature).

Experiences involving the design, installation, and implementation of universal models integrate multiple disciplines, foster cooperative work and mutual learning, and support specialized training of human resources.

One of these developments, the Planetarium for the Blind, presented for the first time in 2011 [2] (Figure 1), is a proposal that aims to bring the sky closer to mostly blind populations through a multi modal experience, by allowing us to raise our arms and, through touch, recognize the constellation forms and stars that appear in them, bringing us closer not only to the fact that the sky is above our heads, but incorporating resources that allow us to distinguish, for example, between the different magnitudes and surface temperatures of the stars. On the other hand, this planetarium is an immersive experience that reproduces the conditions of a night of observation, appealing to the ear (to identify animals of the nocturnal ecosystem), to the touch from the point of view of cutaneous thermal detectors (since at night the temperature is lower than during the day) and smell (because through a series of aromatizations the perfume of grass and earth is perceived, in a country environment). This resource is also adapted for deaf visitors and it is possible to enter in a wheel chair.

Figure 1. Teachers and students with blindness or visual impairments identifying constellations at the Inclusive Planetarium. The image illustrates various aspects of the “starry sky” at the facility, including stars of different magnitudes (represented by size and brightness) and spectral types (representing color and temperature), as shown on the right.

The space of the planetarium (see Figure 2) is prepared to be isolated from the external environment. Their dimensions, 4 m of diameter and 2 m as maximun height at the center of the dome, permits that around 15 pesons assisit to the shows and children can touch all the sky, which represents the starry night from March to June in the Southern Hemisphere.

Figure 2. Two perspectives of the ‘Planetarium for All’ installation, as exhibited at the National Atomic Energy Commission in Mendoza (left) and Tecnópolis (right). The space reproduce the night environment and t is prepared for arounf 15 visitors. It is possible acccess in wheelchair.

Perhaps the most important conclusion about this proposal is that not only do people with disabilities feel included in the experience, but those visitors without obvious disabilities notice the multiple ways in which human beings connect with the world.

The commonly used forms of tactile images consist of 2D (tactile graphics) and 3D (tactile models) representations.

The skin has multiple receptors that permit the tactation, the sensation perceived by the sense of touch. Touch is used in many ways to connect our brain with the environment. The tactile stimulation is linked with mechanoreceptive units, which react to different stimuli, pressure, temperature, and electric signals; in this sense, several works propose different displays to give access to new ways to exchange information with blind and motor-disabled people, mainly, but also deaf people [22].

The key parameters that determine the design of a tactile display for each receptor include:

• sensor spatial resolution and sensitivity,
• temporal processing properties (e.g., adaptation and summation),
• spatial characteristics of sensory processing, and
• information processing delays.

The skin contains several classes of mechanoreceptors with respective sensory modalities. Four types of mechanoreceptors are embedded at different depths within the skin tissue [23,24]. On the palm, Meissner corpuscles (superficial) and Pacinian corpuscles (deep) are located approximately 0.7 mm and 2 mm beneath the surface, respectively. Among these, Merkel cells (pressure), Meissner corpuscles (low-frequency vibration), and Pacinian corpuscles (high-frequency vibration) are the most commonly used in tactile display applications. Merkel cells and Meissner corpuscles are found at depths of 0.7–0.9 mm, while Pacinian corpuscles are deeper, at around 2 mm (see Figure 3).

Figure 3. Diagram of the structure of human skin and tactile receptors (Credit: free license; The colors are only for differentiating strutures).

The microstructure of a surface fundamentally influences its perceptual attributes—specially in terms of the roughness—smoothness spectrum and provides tactile cues essential for the sensory discrimination and identification of materials such as paper, leather, metal, or glass. According to Katz [25], fingers are more sensitive to substance-related properties, such as temperature, hardness, and texture, than to shape-related ones like form, size, weight, or volume. His studies show high accuracy in haptic discrimination of texture and hardness, especially when there is rotational movement between the hand and the surface.

Touch can be categorized as passive or active [26]. Passive touch occurs when the stimulus is applied to a static contact area of the skin. In contrast, active touch involves intentional exploratory movements of the fingers, which are adapted to the type of information being sought.

The tactile perception of specialized symbols and other complex concepts within maps or two-dimensional representations underscores the critical importance of optimizing tactile information. This optimization should be achieved through user-centered design methodologies, ensuring that the message is both accessible and meaningful for diverse users, particularly those with touch as a primary sensory modality. For example, two lines separated by at least 1.3 mm are perceived as separate lines. The optimal elevation for tactile graphics, at which resources are minimized and performance is maximized, appears to be around 200 microns [27]. In this sense, it is important to note that there are areas of the hand with maximum sensitivity and analize how people with a tactile learning modality, which could be all people, use the sensors in the hand. The presence of sensors on the fingers of the hand is notable and are used when perceiving textures, temperatures, elevations, and depressions on surfaces, such as on maps, and even when reading a text in Braille code.

Even taking into account the bibliography, a user-centered desing is needed; the absence of user feedback can lead to the development of materials that fail to effectively convey specific concepts, such as identifying key reference points, understanding spatial relationships, and interpreting the overall structure of a diagram. The mental model of the blind user can not be adjusted to the real world without user-centered design.

Synthesis and Functional Comparison

While the literature discussed above establishes the importance of multimodal tools, most existing developments focus on isolated sensory channels—primarily auditory sonification or static tactile graphics. For instance, projects like sonoUno ([8,13,19]) have revolutionized data interpretation through sound, yet they lack the physical dimensionality required for spatial astronomical concepts. Conversely, traditional tactile maps ([3,4,5,27]) provide spatial structure but fail to convey dynamic physical properties such as stellar temperature or magnitude variation.

The innovation of the present study lies in the simultaneous integration of tactile and thermal stimuli. Unlike previous models that rely on relief alone, our approach utilizes the skin’s thermoreceptors alongside mechanoreceptors to encode complex data (e.g., spectral types of stars). As will be shown in the following sections, this “tactile-thermal” scheme addresses a critical gap in universal design: providing a high-fidelity, immersive experience that simulates the physical reality of a nocturnal observation environment—incorporating temperature drops and thermal gradients that have remained largely unexplored in previous astronomical educational resources.

3. Tactile Models

3.1. Visual and Only-Tactile-Relief Models

Several works have explored the fabrication of objects with tactile properties [28,29], fabricated texture plates from a set of visual textures converted to shallow height maps, asked human subjects to rate the resulting textures according to a set of adjectives (including “rough”), and analysed a set of computational texture features to find those highly correlated with the perceptual scales.

Other work in the fabrication domain has aimed to facilitate the incorporation of tactile properties in 3D printed models. Torres et al. (2015) [30] provide an interface to fabricate objects with user-specified weight, compliant infill, and rough displacement maps. Chen [31] also developed methods to fabricate objects with specified deformation behavior and textured surface displacement. Tymms et al. [32] presented a perceptually based model for evaluating the tactile roughness of surface textures obtained with a 3D printer.

Over the years, different scaled models have been developed in the framework of the present study for the education and dissemination of Astronomy using relief maps of stars. Probably the most widely spread tools are tactile. Users tend to prefer thermoformed and microcapsule paper for tactile representations [33]; however, these materials lack long-term durability. To determine the most effective method for representing stars, asterisms, and accompanying Braille descriptions using a universally accessible technology, multiple trials were conducted with 3D-printed models.

In Figure 4, the constellations of Orion and Scorpius are shown. From the feedback with the users, the representation of the faintest stars was changed, from cylinders to semi-spheres, and for Braille code, the final print was connected with the “best perception” for the blind users. One of the common comments at the moment of detecting the small features on the printed model is about the texture; in the case of Braille, the texts must be felt as soft, easy to touch, and the word used when the perception is not adequate is that the text is perceived as “aggressive”.

Figure 4. Orion (left) and Scorpius (right) asterisms, shown in a 3D-printed representation. Note that Braille text was included as part of the printing process. The constellations are represented as they appear from the Northern Hemisphere.

Due to the limitations of 3D printing for large-scale models—primarily in terms of production time and cost—we investigated alternative representational methods that integrate both tactile and visual components, specifically through the incorporation of LEDs. This includes the electronic control of these lights, which permits an original design involving technicians and engineers. As outlined in Section 1, this exploration led to the development of a specialized planetarium designed mainly for users with visual impairments. It consists of a dome covered with LEDs representing the stars with different sizes (magnitudes). Beyond their primary purpose for visually impaired users, these resources are also appealing to sighted individuals. The LED lighting not only enhances visibility but also conveys additional information—such as color—which can be used to represent the surface temperature of a star in the model [2]. The Planetarium represents the southern sky as seen in May. This choice was made to align with a significant moment in Argentine history, serving as a way to connect astronomy with the sky of a memorable time.

This type of proposal is accessible to the blind, because people can touch the stars and recognize the different patterns (asterisms, constellations), dimension of the represented stars (associated with the magnitude, using the same approach than the used in the star maps) to understand the meaning of the magnitude, a diameter of a circle represents the “brightness” of the star: big, means more bright, small circle reppresents less bright, and then, a fainted stellar object.

3.2. Portable Constellations

Following the development of the planetarium and user feedback, the proposal evolved into individual portable constellations, also equipped with LEDs and designed for use in classrooms or auditoriums (Figure 5). However, the model required improvement, as it is essential for visually impaired individuals to have the opportunity to imagine and experience a realistic environment not only through textures, sizes, and material properties, but also through temperature.

Figure 5. Portable LEDs Tactile Constellations: Scorpius (left) and Orion (right). The stars are represented by LEDs of different sizes (magnitude of the stars) and different colours (temperature of the stars).

3.3. Visual and Tactile-Relief-Thermal Model Implementation

Heat and temperature are also important modalities of the sense of touch. While the skin may seem sensitive to temperature, its receptors do not register absolute temperature values; rather, they respond to the flow of thermal energy. As a result, temperature differences contribute to the qualitative perception of touch. In this context, the ability to perceive two nearby points (e.g., two stars) and the use of varying or similar temperatures increase the effectiveness of this type of device by stimulating different skin actuators (Figure 6).

Experiments have shown that humans can discriminate between spatially distinct thermal stimuli based on the flow of heat perceived through the skin [34,35,36].

Figure 6. Correlation between the multimodal interface’s actuators and the stratified receptors within the skin (Epidermis, Dermis, and Subkutis). Specifically: (i) Thermoelectric elements stimulate temperature receptors to encode spectral data; (ii) Motor movements trigger Meissner and Pacini corpuscles through light touch and vibration; (iii) Folding patterns provide shape and texture cues via Merkel cells and Ruffini corpuscles; and (iv) User movement facilitates kinesthetic perception through the stretching of the skin [37].

Figure 6. Correlation between the multimodal interface’s actuators and the stratified receptors within the skin (Epidermis, Dermis, and Subkutis). Specifically: (i) Thermoelectric elements stimulate temperature receptors to encode spectral data; (ii) Motor movements trigger Meissner and Pacini corpuscles through light touch and vibration; (iii) Folding patterns provide shape and texture cues via Merkel cells and Ruffini corpuscles; and (iv) User movement facilitates kinesthetic perception through the stretching of the skin [37].

A challenge of this kind of development is to include in the model both characteristics: brightness (magnitude) and surface temperature (color of the stars) for blind people. Exploiting the modalities of the skin’s sensors, previously described, the systems implemented so far can be classified into the following major categories based on:

• static pressure (mechanical energy), and
• thermal flow (temperature difference).

The star magnitude concept was solved using different LEDs, which present different sizes, good to explain the concept of magnitudes. In addition, present a set of colors, appropriated to explain surface temperature for not blind people, because the highest temperatures in the star are perceived as blue, and the lower as red, for the blind adaptation was needed to include the tactile perception of the temperature, and this is the base of this innovation.

The following sections describe the design, supplies, and construction of a constellation made with incandescent lamps, which represent stars with different temperatures, including the issue of magnitude.

3.4. Thermal Model: Design and Construction

The design of the thermal model was informed by user feedback from previous multimodal projects, prioritizing ergonomic dimensions and the tactile requirements of diverse users. This development responds to consistent demand observed during years of testing and exhibitions; consequently, we believe a comprehensive description of this resource is essential. In an era dominated by digital interfaces and AI, presenting a hand-on, as the tactile-thermal proposal, is a core objective of our research group. Our goal is not to overlook new technologies, but to highlight the importance of an analog approach to knowledge, recognizing that both digital and physical methods are complementary in achieving a deeper understanding of nature.

Due to its relative simplicity in the stars distribution, the rather well known shape of the “scorpion” and considering the brightest stars (until magnitude 4) and the variety of colors, the Scorpius constellation was chosen to prepare a prototype for a thermal model. Figure 6 shows the constellation and distribution of stars with the identification and color assigned to each object, according to their temperature. Table 1 details the apparent magnitude/brightness and spectral type/color of each selected stellar object.

Table 1. Magnitude and Color equivalences of the brightest stars in Scorpius.

Id Star	Mag	LED Size	SpT/Color
$\alpha$ Sco	1.6	10	M-red
$\lambda$ Sco	1.6	10	B-blue
$\theta$ Sco	1.9	8	A-white/yellow
$\delta$ Sco	2.3	8	B-blue
$ϵ$ Sco	2.3	8	K-red
$\kappa$ Sco	2.4	8	B-blue
$\beta$1 Sco	2.6	5	B-blue
$\nu$ Sco	2.7	5	B-blue
$\tau$ Sco	2.8	5	B-blue
$\pi$ Sco	2.9	5	B-blue
$\sigma$ Sco	3	5	B-blue
$\iota$1 Sco	3	5	F-yellow
$\mu$1 Sco	3	5	B-blue
G Sco	3.2	5	K-red
$\eta$ Sco	3.3	5	F-yellow
$\zeta$2 Sco	3.6	5	K-red

The stars with apparent magnitudes between 1.6 and 3.6, were organized in 3 ranges of the apparent magnitude, assigning the LED diameters (10, 8, and 5 mm); and according to the spectral types, the objects were organized in 3 groups, assigning the colors: blue (high temp.), yellow (intermediate temp), and Red (low temp), as presented in Figure 7 and Table 1. The presence of a supergiant in the group was also taken into account: $\alpha$ Sco (Antares) is the most luminous and brightest star in the constellation (consequently represented by the largest tactile knob in the model) as well as one of the stars with the lowest temperature.

Figure 7. The Scorpion Asterism: haptic constellation design. The stars are indicated with their Bayer identification (Greek letters), where $\alpha$ represents the brightest star in the constellation. The color of the stars are associated with their temperatures, from blue the hottest ones, until red, the coolest ones.

The prototype design includes:

• Thermal Actuators: Incandescent micro-lamps (T5, 12 V/12 W) (Figure 8, left) were used as electrical-to-thermal energy transducers.
• Intensity Control: Temperature modulation was achieved using variable voltage regulators (based on the LM317 integrated circuit), allowing precise calibration of three thermal ranges representative of the spectral classes:
  • Class M (Cold): 27 °C (Simulating red stars).
  • Class G (Medium): 35 °C (Simulating yellow stars).
  • Class O/B (Hot): 45 °C (Simulating blue stars).

Figure 8. T5 car dashboard lamp 12 V/12 W (left); lamp caps: 8mm, 10mm, and 12mm, from left to right (right), made with a 3D printer.

Figure 8. T5 car dashboard lamp 12 V/12 W (left); lamp caps: 8mm, 10mm, and 12mm, from left to right (right), made with a 3D printer.

To represent the stars and cover the lamps, specially designed caps were 3D printed, taking into account three different measurements: 8 mm, 10 mm and 12 mm (Figure 8, right) and using 3 different colors: red, blue and yellow, which covers the set of stars selected in the constellation. Each cap is 15 mm high, allowing the same lamp to be used for all magnitudes of stars involved. ABS material was used for the lamp caps due its high strength and heat resistanceas, Ideal for functional parts requiring high impact resistance, including electronics enclosures and toys. Moreover, it has a melting temperature above 200 °C, which prevents the plastic damage when the lamp reaches 55 °C on its surface, the maximum temperature programmed for the model.

3.5. User Interface

The final scaled model of the Scorpius constellation is presented in Figure 9: the box dimensions (left), which can be considered as a “haptic interaction matrix” with specific dimensions, enabling bimanual scanning and different magnitudes-size and surface temperature-colors (right).

Figure 9. Haptic interface of the thermal constellation, with dimensions expressed in millimeters (left); the final thermal Scorpius constellation model (right). The dimensions of the box was decided after several proofs with users.

To summarize the development and its potential value, this haptic model incorporates tactile-shape and tactile-thermal information simultaneously. It attempts to replicate, as closely as possible, the perception of The Starry Night that sighted individuals experience when perceiving the brightness and colors of stars visually. We have translated the perception of fundamental astronomical data—such as magnitude and spectral types—to the skin, utilizing multiple skin receptors to achieve this.

In the next section, we will test and evaluate the impact of this proposal on the ability of users, particularly those who are blind, to recognize several characteristics of astronomical data at once.

4. Testing the Haptic Interface

In sensory design, it is essential to enable visually impaired individuals to perceive spatial atmospheres through different textures, temperatures, and material qualities. The skin translates tactile stimuli into neurochemical signals that support both mental imagery and emotional responses [38,39]. Higher material fidelity improves the accuracy of these internal representations. Therefore, realism in tactile models is key to effectively conveying environmental experience.

To evaluate the thermal performance of the model and the thermal perception of blind and sighted users, several tests were conducted. The final version of the model was presented in high-impact exhibitions previously the study presented in this article (see Figure 10 and Figure 11). Observations and public satisfaction surveys allow us to develop formal methods for evaluating the impact of these tools. Furthermore, they help refine the materials, initially on an individual, sensory level to evolve toward a multimodal experience.

Figure 10. Blind people testing the thermal constellation at The Invisible Factory exhibition, Mendoza, Argentina, July 2019.

Figure 11. Different visitors in the XXX IAU General Assembly, testing the haptic interface for Scorpius, during the 1st IAU-Inspiring Stars exhibition. Vienna, August 2018.

Active touch enables up to 95% accuracy in perceiving abstract or unfamiliar objects, whereas passive touch yields only approximately 45% accuracy [40]. However, passive touch remains essential for detecting temperature fluctuations and differences. In both instances, the tactile system must integrate information acquired progressively across multiple dimensions.

From a neurophysiological perspective, the interface addresses two important aspects:

• Selective Stimulation: The design leverages the high density of Meissner’s corpuscles and Merkel discs in the fingertips for texture discrimination (representing magnitude), while thermoreceptors (C and A-delta fibers) decode spectral information (representing color)
• Kinesthetic Perception: By utilizing the Scorpius asterism, the interface encourages kinematic exploration, allowing users to construct a spatial mental map based on the relative positions of the actuators.

Experience gained from exhibitions and outreach activities with very hetherogeneus audiencies, which involves sight, blind al low vision people, with differnt bacckground, ages and habilities, confirms that users can perceive subtle thermal differences between materials through touch, even when absolute temperature variations are minimal. This multimodality is valuable not only for blind individuals but also for those who are color-blind or visually impaired, as it helps convey the relationship between color and temperature. Furthermore, multimodality significantly benefits users with a predominantly visual learning profile.

4.1. A New User Test: The Thermal Interface as Part of a Multimodal Approach

The present user study permitted us to advance one more step, involving a specific and diverse cohort (n = 20) to ensure a broad spectrum of tactile and thermal perception in a controlled environment. Participants were categorized at the beginning of the test described in the next section, by visual condition (total blindness, low vision, and sighted) and, crucially, by their prior experience with tactile educational resources. From the initial group of participants we decided to concentrate the pilot survey in the core of n = 6 (5 blind and 1 low vision), all of them with a background in tactile recognition in Braille. The participants had no previous training in tactile maps or astronomical models. Educational backgrounds range from secondary school to university level, we respect a balance in gender and ages between 20 and 60, ensuring the multimodal interface’s accessibility across different cognitive stages. Previous to this particular activity, astronomical contents were transmitted, for example the history of the constellations and the meaning of concepts such as power/brightness and temperature/color as well as the importance of these data in the scientific research.

4.2. Technical Limitations of the Prototype

The main challenges to be addressed for the tactile-thermal “hardware”, can be summarized as:

• Thermal Range: The stars operate at an intermediate temperature and the differences can be recognized by the users
• Response Time: The temperature is stabilized a few seconds, because the lamps used and no significant changes were reported by the user along with a full recognition of the model. However, sustaining precise thermal gradients over long-duration exhibitions remains a technical hurdle for future iterations.
• Spatial Resolution: The distance between the tactile actuators permits to have a comfortable model, ideal to detect the “stars” alone and the full asterism.

The experience gained after the exhibitions of the prototype, permitted us to adjust these main key parameters.

5. Pilot Qualitative Study with a Target User Group

Building on the experiences described in the previous section, the multimodal study (2025) was conducted. This study integrated tactile-relief, tactile-thermal, and auditory resources, including transducer devices that transform color into sound. The activities were organized into three-hour workshops, held once a week over two months. This experience was vital not only for understanding how the brain organizes information across different senses but also for reinforcing the original thesis regarding the importance of a multimodal approach to nature (Figure 12 and Figure 13).

Figure 12. Participants with blindness identifying magnitudes and temperatures using two distinct models of Scorpius: a multimodal model representing magnitude and color-to-temperature (left), and a non-thermal tactile LED constellation designed solely for brightness detection (right). (Sensory Stimulation Training Course, November 2025).

Figure 13. Blind people comparing thermal levels on the multimodal constellation of Scorpius, to recognize colors, and identifying magnitudes, through the caps sizes. (Sensory Stimulation Training Course, November 2025).

Participants underwent a free exploration phase followed by a guided identification task. An initial workshop was conducted with 20 participants to evaluate preliminary interactions.

For the pilot qualitative analysis of cognitive load and diagnostic accuracy, a core group of six Blind and Low-Vision (BLV) participants was selected to complete a full usability assessment. Their responses facilitated the identification of critical patterns in thermal perception and basic asterism recognition.

This study was designed as a qualitative usability pilot for a novel multimodal thermal device rather than a large-scale statistical validation. Within the fields of Assistive Technology and Human-Computer Interaction (HCI)—particularly when engaging with specialized populations like the BLV community, a sample size of n = 6 is widely recognized as sufficient for identifying primary usability barriers, validating a “proof-of-concept,” and uncovering the majority of core interaction issues in high-fidelity prototypes. Consequently, this sample size provides a robust foundation for assessing the device’s functional viability and informing future iterative designs.

To complete this pilot study, we introduced data sonification as well as the transduction of magnitude (brightness) and temperature/color into sound. This was made possible through the use of the sonoUno software [15], the LightSound device [41] and a prototype of the Orchestar [42].

While the LightSound was originally designed for use during eclipses, and the Orchestar allows for the transformation of color into sound, both devices transduced the specific elements critical to this experience:

• Magnitude: Sound frequency changes from low (for faint stars) to high (for bright stars).
• Color/Temperature: Star colors are transformed into sound according to a specific scale, where red (low temperature) corresponds to low frequency and blue (high temperature) corresponds to high frequency.

Additionally, examples of extended astronomical objects, such as nebulae, were presented. In these instances, full-color images (featuring high contrast and resolution for sonification) were used alongside tactile 3D-printed models of the same objects.

Although the questions regarding the thermal constellation were the primary focus of this study, the entire study is presented here as it was conducted in a combined manner to allow for comparison between modalities. To ensure the validity and reliability of the results, a Reflective Thematic Analysis was employed, allowing patterns associated with specific themes to be identified through the collected responses.

Beyond the spontaneous comments made by participants during the experience (which were also recorded), the following specific questions were asked:

• What did you think of the multimodal materials you used?
• What is your opinion about the relief map of the constellations?
• What is your opinion about the thermal constellation?
• Are there any aspects you would like to see improved?
• What do you think you have learned from these models?
• What would you change about their presentation?
• Do you prefer models that are only tactile, or does the addition of thermal elements aid understanding?
• What do you think about the sound effects for the colors of the stars or nebulae?
• Did working with these models change your relationship with astronomy or your understanding of science?

The raw information, presented in Table 2 and Table 3, was processed according to the following methodology:

• Transcription and Identification: Responses were reviewed (including audio-to-text transcriptions where necessary) to identify units of meaning based on the participants’ perceptions of tactile, thermal, and auditory stimuli.
• Thematic Grouping: Common themes were organized into three primary dimensions:

  -

  Usability (simplicity, novelty, synergy between senses).

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  Pedagogical effectiveness (understanding and learning of scientific concepts).

  -

  Emotional impact (inclusion, perception of science).

• Multimodal Analysis: An analysis of multimodality was performed by comparing simple and combined stimulus models, involving multiple senses such as relief only, relief-thermal, and relief-sound;
• Refinement Inquiry: Finally, an assessment was conducted regarding difficulties encountered, as well as identified needs for changes or improvements.

Table 2. User Experience and sensorial dimensions: participants testimonies.

ID	Complete Answer	User Experience/Sensorial Dimension
		Tactile	Thermal	Sonification	Synergy
U1	“I thought the sky was off-limits to us, but it wasn’t. Working with these models made me feel included…”	I thought they were very good.	The thermal component completes the touch model.	Sound was very effective for learning concepts like color.	I thought the combination of materials was perfect.
U2	“Before learning about these models, I thought astronomy was impossible for us…”	I thought the materials were perfect.	The thermal aspect was innovative.	Sound complements the other senses.	A perfect combination.
U3	“I had never thought that there are many things that blind people cannot even imagine…”	I thought the materials were wonderful.	The thermal feature was the icing on the cake!	It is very interesting.	I saw more by touching than by looking at the sky!
U4	“Until now, astronomy was, in my opinion, a science for experts…”	Very useful.	Interesting.	I didn’t know the possibility of sound reinforcement existed.	I thought the multisensory materials were good.
U5	“Working with these models changed my relationship with astronomy and science…”	The relief map helped a lot to understand the constellations.	The thermal constellations helped to identify colors.	The sound system is very effective for understanding brightness.	Method helped to build a mental image of the objects.
U6	“I learned things I never imagined I could learn.”	Good.	The combination of tactile relief with thermal sensations was enriching.	Interesting, because I’d never heard of such data before.	The multisensory proposal is very exciting.

Table 2. User Experience and sensorial dimensions: participants testimonies.

ID	Complete Answer	User Experience/Sensorial Dimension
		Tactile	Thermal	Sonification	Synergy
U1	“I thought the sky was off-limits to us, but it wasn’t. Working with these models made me feel included…”	I thought they were very good.	The thermal component completes the touch model.	Sound was very effective for learning concepts like color.	I thought the combination of materials was perfect.
U2	“Before learning about these models, I thought astronomy was impossible for us…”	I thought the materials were perfect.	The thermal aspect was innovative.	Sound complements the other senses.	A perfect combination.
U3	“I had never thought that there are many things that blind people cannot even imagine…”	I thought the materials were wonderful.	The thermal feature was the icing on the cake!	It is very interesting.	I saw more by touching than by looking at the sky!
U4	“Until now, astronomy was, in my opinion, a science for experts…”	Very useful.	Interesting.	I didn’t know the possibility of sound reinforcement existed.	I thought the multisensory materials were good.
U5	“Working with these models changed my relationship with astronomy and science…”	The relief map helped a lot to understand the constellations.	The thermal constellations helped to identify colors.	The sound system is very effective for understanding brightness.	Method helped to build a mental image of the objects.
U6	“I learned things I never imagined I could learn.”	Good.	The combination of tactile relief with thermal sensations was enriching.	Interesting, because I’d never heard of such data before.	The multisensory proposal is very exciting.

Table 3. Focus-group impact study: congnitive and emotional dimensiones, improvement and critics.

ID	Cognitive Dimension			Emotional Dimension			Improvement
	New Learning	Understand Structures	Ideas About Astronomy	Interest	Inclusion	Science Vision	Critics
U1	Understood color/temp relationship.	Interested in galaxies and nebulae shapes.	Changed many concepts.	Exceeded expectations.	Felt totally included.	Now I know I can understand the universe.	Nothing to change.
U2	Improved perception of stars.	Sound effects allowed knowing what nebulae are like.	Brought abstract topics closer.	Very interesting proposal.	Felt very included.	Changed perception of science in general.	Nothing to change.
U3	Corrected bad concepts in all topics.	—	Eye-opening to realize past errors.	Felt very motivated.	“I could see, and I felt very included.”	Changed my view of science.	Nothing to change.
U4	Constellations topic was new and enriching.	Interpreted through touch.	As an artist, learned true color formation.	Inspired to communicate to others.	Felt very comfortable.	Learned to see from another perspective.	Add smell and tactile signage.
U5	Relationship between brightness, distance and color.	Recognized extended objects like nebulae.	Changed relationship with research.	Very excited to know more.	Felt very included.	Changed relationship with science.	More time for exploration.
U6	Novel topics related to celestial objects.	—	Sound effects for chemical composition.	Enriching experience.	Felt very included.	Made me think beyond the workshop.	Loved the course.

Table 3. Focus-group impact study: congnitive and emotional dimensiones, improvement and critics.

ID	Cognitive Dimension			Emotional Dimension			Improvement
	New Learning	Understand Structures	Ideas About Astronomy	Interest	Inclusion	Science Vision	Critics
U1	Understood color/temp relationship.	Interested in galaxies and nebulae shapes.	Changed many concepts.	Exceeded expectations.	Felt totally included.	Now I know I can understand the universe.	Nothing to change.
U2	Improved perception of stars.	Sound effects allowed knowing what nebulae are like.	Brought abstract topics closer.	Very interesting proposal.	Felt very included.	Changed perception of science in general.	Nothing to change.
U3	Corrected bad concepts in all topics.	—	Eye-opening to realize past errors.	Felt very motivated.	“I could see, and I felt very included.”	Changed my view of science.	Nothing to change.
U4	Constellations topic was new and enriching.	Interpreted through touch.	As an artist, learned true color formation.	Inspired to communicate to others.	Felt very comfortable.	Learned to see from another perspective.	Add smell and tactile signage.
U5	Relationship between brightness, distance and color.	Recognized extended objects like nebulae.	Changed relationship with research.	Very excited to know more.	Felt very included.	Changed relationship with science.	More time for exploration.
U6	Novel topics related to celestial objects.	—	Sound effects for chemical composition.	Enriching experience.	Felt very included.	Made me think beyond the workshop.	Loved the course.

Data from the raw responses were categorized using tables and matrices to derive the final numerical results.

Results of the Pilot Study

The study analyzed not only the sensory experience itself, but also the effectiveness of multimodality, concept learning, whether the experience could be improved, and whether it had an impact that modified prior ideas about science.

In this way, perceptual, cognitive, emotional, continuous improvement, and inclusion aspects were addressed:

• In the sensory dimension, tactile, thermal, and auditory models, as well as multimodal synergy (Table 2), were explored. The participants acknowledged the undeniable impact of the thermal model and multimodal synergy. Regarding tactile perception, its usefulness was recognized in all cases, most of the responses indicated a need for this model to complete the image of what was being represented. It should be noted that some of the respondents were not blind.
• In the cognitive dimension (Table 3), the participants improved upon previously acquired concepts or gained new knowledge. By working with specific aspects related to celestial objects, it was possible to quickly assess the learning; concepts such as brightness-distance, color-temperature, and color-chemical composition were clearly understood, and participants commented on how they transferred their “new” knowledge to others.
• Regarding the emotional dimension (Table 3), the high impact of the proposal in terms of interest and inclusion is noteworthy. The participants unanimously declared interest and amazement at the experience and felt completely included; they changed their idea regarding astronomy, which they considered a science forbidden to blind people, and about science in general, stating that the workshop ‘had made them think and become interested in topics related to research’.

Some of the most remarkable comments, as reflected in the survey, were:

‘I thought the sky was off-limits to us, but it wasn’t. Working with these models made me feel included, included in science, and changed my whole perspective, showing me that I could access this knowledge. I felt like I was entering such a beautiful yet mysterious world’.

‘Before learning about these models, I thought astronomy was impossible for us, except perhaps through documentaries. These models changed my perception of astronomy and science. It’s very clever to incorporate thermal and sound data, which are fundamental for us. Regarding science, this can help change other aspects; it could be a starting point for accessing other topics’.

‘It was eye-opening to see how many mistakes I had made, and in some ways, I wish I had had the knowledge from the beginning so I wouldn’t have wasted that time. I love that I’m not the same person I was when I started the workshop’.

Based on the qualitative results, it is possible to derive quantitative frequency data by applying specific indicators, such as “Satisfaction in stimulus distinction”, “Stimulus complementarity to distinguish phenomena” or “Change of vision regarding science”. Table 4 details the results of this analysis.

Table 4. Analysis of indicators, categories, and frequency of success in the multimodal activity.

Indicator	Category	Freq. (n)	%
Satisfaction in stimulus distinction	Tactile Dimension	5/6	83%
	Thermal Dimension	6/6	100%
	Sound Dimension	6/6	100%
Stimulus complementarity to distinguish phenomena	Multisensory Synergy	6/6	100%
New concepts learned	New Concept	6/6	100%
Structure detection	Structures	4/6	67%
Change of ideas about astronomy	Change of ideas about astronomy	6/6	100%
Increased interest in the topic	Interest	6/6	100%
Perception of greater inclusion	Inclusion	6/6	100%
Change of vision regarding science	Scientific Vision	6/6	100%
Improvement suggestions	Improvements	2/6	33%

The most significant findings indicate that 100% of the participants agreed that there is a clear complementarity between stimuli in distinguishing phenomena; in this sense the comments connected with the thermal dimension are that ‘The thermal component completes the touch model’ and ‘it was innovative’. About the multimodal dimension, the participants think that “the Method helped to build a mental image of the constellations”. Through these models, participants reported feeling included in the scientific community, which shifted their perspectives regarding their ability to access knowledge and improved their overall perception of science (‘I thought the sky was off-limits to us, but it wasn’t’, ‘Working with these models changed my relationship with astronomy and science’).

Conversely, 67% of participants were able to detect more extended structures (like interstellar nebulae), while 33% suggested improvements, such as dedicating more time to each experience and incorporating activities that involve the sense of smell: more senses, not less.

As is typical for such proposals, this study considers potential improvements. Some participants suggested incorporating the sense of smell into the multimodal approach and dedicating more time to each workshop to enhance learning. Notably, there were no reports of exhaustion or difficulty in understanding the content. Given the heterogeneity of the participant group, the responses remained free of the biases that might be held by individuals trained in the discipline or by members of the research team.

It was also noted that certain responses echoed those from previous studies and other international experiences [6,19]. Expressions such as, “I never imagined that astronomy was also for us,” and “the combination of resources involving different senses is novel and helps in understanding concepts with less cognitive effort,” are frequently repeated across different activities and audiences.

6. Conclusions

In all cases, participants highlighted the simplicity of the models. The presentation of data using sound (though not a central objective of this study) was a novelty for most attendees. According to their feedback, this did not increase the mental effort required for comprehension—especially for blind participants, for whom hearing is a primary sense. For example, users could identify a cool and brightest star in Scorpius (Antares) while simultaneously recognizing the shape of the constellation.

From an emotional perspective, the proposal had a significantly positive impact. Attendees expressed a desire to participate in similar experiences again, which is fundamental if multimodal models are to be integrated into spaces such as museums and exhibitions. There was also a positive response from sighted individuals, who noted that using more than one sense improves the comprehension and long-term retention of both familiar and new concepts.

The personal growth of the participants was evident in comments such as: “Until now, astronomy was a science for experts. After the workshop, I felt encouraged to share my knowledge with others, and that’s what inclusion is all about.”

We have initiated the development of a series of diagnostic activities to implement training sessions for various age groups and environments (classrooms, museums, and general exhibitions). These are designed to enhance “spatial awareness” for blind individuals through tasks such as: selecting and later relocating specific points, detecting the orientation of lines on a plane, replicating angles, measuring distances, recognizing values in a 2D plot, and organizing proximal points or lines to produce a mental image. These skills are intended to help users navigate a graphics-based world independently.

One significant and relatively new outcome of the activity was the discussion and informal ranking of modern mobile tools, such as Seeing AI (a free visual assistant for the blind and low-vision community developed by Microsoft). This app allows users to transform light intensity into sound, scan barcodes to identify products, and recognize faces. The field of assistive apps represents a vital new line of research for training; many in the community are unaware of available resources or do not yet know how to use them effectively.

The next phase of this work will implement new strategies to investigate human cognition, decision-making processes, and the physiological impact of ‘alternative visualizations’ of complex, non-spatial data. This will be conducted within a controlled experimental environment (such as a Planetarium) utilizing various methods of sensory exploration. Ultimately, our vision for a ‘science for all’ encompasses several key objectives: extending multimodality to complex astronomical objects like galaxies and nebulae; enhancing the study of signal perception—specifically for subtle variations like those in the Cosmic Microwave Background (CMB); training individuals to recognize data through multisensory integration; and advancing the technical capabilities of both hardware and software transducers.