In News:

The Indian Institute of Astrophysics (IIA) recently marked 10 years of successful operations of the UltraViolet Imaging Telescope (UVIT) aboard AstroSat, highlighting India’s achievements in space-based ultraviolet astronomy.

About AstroSat

AstroSat is India’s first dedicated astronomy satellite, designed to study celestial objects across multiple wavelengths simultaneously. It enables coordinated observations in ultraviolet (UV), optical, and X-ray bands, making it comparable to international space observatories.

• Launched: 28 September 2015 by ISRO
• Type: Multi-wavelength space observatory
• Orbit Control: Managed by the Mission Operations Complex (MOX) at ISRO’s ISTRAC, Bengaluru
• Significance: Allows simultaneous study of high-energy cosmic processes with a single platform

Scientific Payloads on AstroSat

AstroSat carries five instruments, each designed to observe different energy bands:

1. UltraViolet Imaging Telescope (UVIT) – Observes in near-UV, far-UV, and visible wavelengths
2. Large Area X-ray Proportional Counter (LAXPC) – Studies high-energy X-ray sources
3. Cadmium–Zinc–Telluride Imager (CZTI) – Detects hard X-rays and gamma-ray bursts
4. Soft X-ray Telescope (SXT) – Observes low-energy X-rays
5. Scanning Sky Monitor (SSM) – Monitors variable X-ray sources across the sky

Together, these cover an energy range of roughly 0.3 keV to 100 keV, along with ultraviolet and limited optical bands.

UltraViolet Imaging Telescope (UVIT)

UVIT is one of the mission’s flagship instruments and was designed and developed by the Indian Institute of Astrophysics (IIA).

• Comprises two telescopes:
  • One for near-UV and visible
  • One for far-UV
• UV observations must be done from space because Earth’s atmosphere absorbs ultraviolet radiation
• Provides high spatial resolution (≈1.5 arcseconds) with a relatively wide field of view

Over a decade of operation, UVIT has:

• Observed over 1,400 celestial targets
• Contributed to hundreds of scientific research papers and multiple PhD theses
• Provided key insights into stars, star clusters, galaxies, and energetic cosmic phenomena

UVIT data products are made available through ISRO’s PRADAN data archive for the global scientific community.

Scientific Objectives of AstroSat

AstroSat was designed to address major questions in high-energy and stellar astrophysics:

• Study high-energy processes in systems containing neutron stars and black holes
• Estimate magnetic fields of neutron stars
• Investigate star formation regions
• Observe X-ray binaries and transient X-ray sources
• Conduct deep-field surveys in the ultraviolet
• Examine active galactic nuclei (AGN) and distant galaxies

Major Scientific Contributions

Observations from UVIT and other payloads have enabled studies such as:

• Identification of hot companion stars in binary systems
• Study of blue straggler stars in clusters
• Mapping extended UV disks in dwarf galaxies
• Observations of novae in the Andromeda galaxy
• Detection of UV emission from distant galaxies
• Understanding links between UV and X-ray activity in active galaxies

Institutional Collaboration

AstroSat was developed through a national collaboration, involving:

• ISRO centres
• Indian Institute of Astrophysics (IIA)
• IUCAA (Pune)
• TIFR (Mumbai)
• International support including the Canadian Space Agency

Future Outlook

Experience gained from UVIT is feeding into plans for INSIST (Indian Spectroscopic and Imaging Space Telescope), a proposed next-generation space observatory to expand India’s capabilities in ultraviolet and optical astronomy.

In News:

India’s first dedicated Space Astronomy Observatory — AstroSat — has successfully completed a decade of operations since its launch on September 28, 2015. Designed for a mission life of five years, AstroSatcontinues to deliver valuable scientific data, marking a major milestone in India’s advancement in space-based astrophysics research.

About AstroSat

• Launched by: Indian Space Research Organisation (ISRO)
• Launch Vehicle: PSLV-C30 (XL)
• Launch Site: Satish Dhawan Space Centre (SDSC), Sriharikota
• Launch Date: September 28, 2015
• Mission Life: Originally 5 years, extended due to sustained functionality and scientific output
• Managed by:Mission Operations Complex (MOX) of ISTRAC, Bengaluru

AstroSat represents India’s first multi-wavelength space observatory, capable of observing celestial bodies in Visible, Ultraviolet (UV), and low and high-energy X-ray bands of the electromagnetic spectrum simultaneously — a capability possessed by only a handful of space observatories globally.

Scientific Objectives

AstroSat was conceived to advance India’s capability in space-based astronomy and to deepen understanding of high-energy astrophysical phenomena. Its key scientific goals include:

• Investigating high-energy processes in binary star systems containing neutron stars and black holes.
• Estimating magnetic field strengths of neutron stars.
• Studying star formation regions and energetic star systems beyond the Milky Way.
• Detecting and monitoring transient X-ray sources (brief, bright cosmic events).
• Conducting a limited deep-field survey of the universe in the ultraviolet region.

Key Instruments (Payloads)

AstroSat carries five scientific payloads, each contributing to multi-spectral observations:

• Ultra Violet Imaging Telescope (UVIT):Observes celestial objects in near and far ultraviolet as well as visible wavelengths, helping in the study of star formation and evolution.
• Large Area X-ray Proportional Counter (LAXPC):Detects time variability and spectral properties of X-ray sources in the 3–80 keV range.
• Cadmium–Zinc–Telluride Imager (CZTI):Observes hard X-rays (above 20 keV) and helps study gamma-ray bursts and black hole emissions.
• Soft X-ray Telescope (SXT):Provides soft X-ray imaging and spectroscopy to study compact objects like neutron stars and white dwarfs.
• Scanning Sky Monitor (SSM):Continuously scans the sky to detect new transient X-ray sources and track their variability.

Why is it in the News?

India’s first multi-wavelength space-based observatory, AstroSat, has detected intense sub-second X-ray bursts emanating from a neutron star with an ultrahigh magnetic field, known as a magnetar.

What is X-ray Bursts?

• X-ray bursts manifest in low-mass X-ray binary systems featuring a neutron star and a low-mass main sequence star orbiting each other.
• The occurrence of these bursts is intricately linked to the gravitational dynamics of the neutron star and its companion.
• In this system, the proximity and intense gravitational forces of the neutron star cause the companion star to exceed its Roche-lobe, leading to the formation of an accretion disk around the neutron star.
• This disk becomes a repository for hydrogen drawn from the overflowing companion star.
• As hydrogen accumulates on the neutron star's surface, the extreme temperatures and pressures prevailing there catalyze its transformation into helium.
• This ongoing process results in the formation of a thin surface layer of helium.
• When this helium layer reaches a critical mass, a sudden explosive ignition occurs, elevating the entire neutron star's surface temperature to several tens of millions of degrees and releasing a burst of X-rays.
• Following the outburst, the binary system returns temporarily to a quiescent state, allowing the neutron star to reaccumulate the helium surface layer gradually.
• This cyclic process leads to the recurrence of X-ray bursts, typically unfolding at regular intervals separated by several hours or days.

About Indias’ AstroSat:

• AstroSat stands as India’s first dedicated multi-wavelength space observatory, pioneering a mission focused on the simultaneous study of celestial sources across X-ray, optical, and UV spectral bands.
• Launched with a lift-off mass of 1515 kg, AstroSat took flight aboard the Indian launch vehicle PSLV from the Satish Dhawan Space Centre in Sriharikota on September 28, 2015.
• It entered a 650 km orbit, inclined at an angle of 6 degrees to the equator.
• The Mission Operations Complex (MOX) at ISRO Telemetry, Tracking and Command Network (ISTRAC) in Bengaluru oversees the satellite throughout its mission life.
• With a minimum useful life of around 5 years, AstroSat is dedicated to achieving the following scientific objectives:
  • Understanding high-energy processes in binary star systems housing neutron stars and black holes.
  • Estimating magnetic fields associated with neutron stars.
  • Investigating star birth regions and high-energy processes in star systems beyond our galaxy.
  • Detecting new, briefly bright X-ray sources in the celestial sphere.
  • Conducting a limited deep-field survey of the Universe in the Ultraviolet region.

Why is it in the News?

India's AstroSat space telescope has achieved a significant milestone by detecting more than 600 Gamma-Ray Burst (GRB), each marking the death of a massive star or merging of neutron stars.

About ISRO’s AstroSat:

• AstroSat is the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, optical, and UV spectral bands simultaneously.
• One of the unique features of the AstroSat mission is that it enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite.
• AstroSat, with a lift-off mass of 1515 kg, was launched by the Indian launch vehicle PSLV from Satish Dhawan Space Centre, Sriharikota, on September 28, 2015, into a 650 km orbit inclined at an angle of 6 degrees to the equator.
• The minimum useful life of the AstroSat mission is expected to be 5 years.
• It carried a total of five scientific payloads, enabling imaging and studying the temporal and spectral properties of galactic and extra-galactic cosmic sources in a wide range of wavelengths on a common platform.
• The scientific objectives of AstroSat’s mission are:
• To understand high energy processes in binary star systems containing neutron stars and black holes.
• Estimate magnetic fields of neutron stars.
• Study star birth regions and high energy processes in star systems lying beyond our galaxy.
• Detect new briefly bright X-ray sources in the sky.
• Perform a limited deep-field survey of the Universe in the Ultraviolet region.
• At present, all the payloads are operational and are observing the cosmic sources.