Indus constellation is located in the southern hemisphere. It is the 49th constellation in size, occupying an area of 294 square degrees. It lies in the fourth quadrant of the southern hemisphere (SQ4) and can be seen at latitudes between +15° and -90°. The neighboring constellations are Grus, Microscopium, Octans, Pavo, Sagittarius, Telescopium and Tucana.
[http://www.constellation-guide.com/constellation-list/indus-constellation/]
Indus and Pavo in Corbinianus Thomas, Firmamentum firmianum, 1730
[http://www.constellationsofwords.com/Constellations/Indus.htm]
The constellation was one of twelve created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm diameter celestial globe published in 1597 (or 1598) in Amsterdam by Plancius with Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer’s Uranometria of 1603. Plancius portrayed the figure as a nude male with arrows in both hands but no bow.
Constellations of Indus and Grus
[https://www.davidmalin.com/fujii/source/Ind.html]
[http://www.dibonsmith.com/ind_con.gif]
Indus does not contain any bright stars. Alpha Indi is a third magnitude giant star, located about 98 light years from the Earth. The stellar classification of this star is K0 III-IV, so it has exhausted the hydrogen at its core and evolved away from the main sequence. It has about double the mass of the Sun and is an estimated billion years old. As a giant star it has expanded to about 12 times the radius of the Sun. The effective temperature of the photosphere is 4,893 K, giving it the characteristic orange hue of a K-type star. It may have two nearby M-type companion stars, which are located at least 2,000 Astronomical Units from the primary.
[https://en.wikipedia.org/wiki/Alpha_Indi]
Beta Indi is a K-type bright giant star, with an apparent visual magnitude of approximately 3.658. It has a visual companion, CCDM J20548-5827B, with an apparent visual magnitude of approximately 12.5. It is located 600 light-years from Earth.
[https://en.wikipedia.org/wiki/Beta_Indi]
Epsilon Indi is a star system approximately 12 light-years from Earth in the constellation of Indus consisting of a spectral type K4.5V main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it. The brown dwarfs were discovered in 2003. ε Indi Ba is an early T dwarf (T1) and ε Indi Bb a late T dwarf (T6) separated by 0.6 arcseconds, with a projected distance of 1460 AU from their primary star.
Epsilon Indi A has only about three-fourths the mass of the Sun. Its surface gravity is slightly higher than the Sun’s. The metallicity of a star is the proportion of elements with higher atomic numbers than helium, being typically represented by the ratio of iron to hydrogen compared to the same ratio for the Sun; Epsilon Indi A is found to have about 87% of the Sun’s proportion of iron in its photosphere.
The corona of Epsilon Indi A is similar to the Sun, with an X-ray luminosity of 2×10^27 ergs s^−1 and an estimated coronal temperature of 2×10^6 K. The stellar wind of this star expands outward, producing a bow shock at a distance of 63 AU. Downstream of the bow, the termination shock reaches as far as 140 AU from the star.
This star has the third highest proper motion of any star visible to the unaided eye, after Groombridge 1830 and 61 Cygni, and the ninth highest overall. This motion will move the star into the constellation Tucana around 2640 AD. Epsilon Indi A has a space velocity relative to the Sun of 86 km/s, which is unusually high for what is considered a young star. It is thought to be a member of the ε Indi moving group of at least sixteen population I stars. This is an association of stars that have similar space velocity vectors, and therefore most likely formed at the same time and location.
Artist’s conception of the Epsilon Indi system showing Epsilon Indi A and its brown-dwarf binary companions.
In January 2003, astronomers announced the discovery of a brown dwarf with a mass of 40 to 60 Jupiter masses in orbit around Epsilon Indi A at a distance of at least 1,500 AU. In August 2003, astronomers discovered that this brown dwarf was actually a binary brown dwarf, with an apparent separation of 2.1 AU and an orbital period of about 15 years. Both brown dwarfs are of spectral class T; the more massive component, Epsilon Indi Ba, is of spectral type T1–T1.5 and the less massive component, Epsilon Indi Bb, of spectral type T6.
Evolutionary models have been used to estimate the physical properties of these brown dwarfs from spectroscopic and photometric measurements. These yield masses of 47 ± 10 and 28 ± 7 times the mass of Jupiter, and radii of 0.091 ± 0.005 and 0.096 ± 0.005 solar radii, for Epsilon Indi Ba and Epsilon Indi Bb, respectively. The effective temperatures are 1300–1340 K and 880–940 K, while the log g (cm s^−1) surface gravities are 5.50 and 5.25, and their luminosities are 1.9 × 10^−5 and 4.5 × 10^−6 the luminosity of the Sun. They have an estimated metallicity of [M/H] = –0.2.
Measurements of the radial velocity of Epsilon Indi (2002) appear to show a trend that indicated the presence of a planetary companion with an orbital period of more than 20 years. A substellar object with minimum mass of 1.6 Jupiter masses and orbital separation of roughly 6.5 AU could explain the observed trend. If confirmed, it would be a true Jupiter-analogue.
A visual search using the ESO’s Very Large Telescope found one potential candidate. However, a subsequent examination by the Hubble Space Telescope NICMOS showed that this was a background object. As of 2009, a search for an unseen companion at 4 μm failed to detect an orbiting object. These observations further constrained the hypothetical object to be 5–20 times the mass of Jupiter, orbiting between 10–20 AU and have an inclination of more than 20°. Alternatively, it may be an exotic stellar remnant.
No excess infrared radiation that would indicate a debris disk has been detected around Epsilon Indi. Such a debris disk could be formed from the collisions of planetesimals that survive from the early period of the star's protoplanetary disk.
During Project Ozma in 1960, this star was examined for artificial radio signals, but none were found. In 1972, the Copernicus satellite was used to examine this star for the emission of ultraviolet laser signals. Again, the result was negative. Epsilon Indi leads a list of 17,129 nearby stars most likely to have planets that could support complex life.
The sun from Epsilon Indi
[https://commons.wikimedia.org/wiki/File:Sun_from_Epsilon_Indi.jpg]
As seen from Epsilon Indi, the Sun is a 2.6-magnitude star in Ursa Major, near the bowl of the Big Dipper.
[https://en.wikipedia.org/wiki/Epsilon_Indi]
Indus is home to one bright binary star. Theta Indi is a binary star divisible in small amateur telescopes, 97 light-years from Earth. Its primary is a white star of magnitude 4.5 and its secondary is a white star of magnitude 7.0.
T Indi is the only bright variable star in Indus. It is a semi-regular, deeply coloured red giant with a period of 11 months, 1900 light-years from Earth. Its minimum magnitude is 7 and its maximum magnitude is 5.
Galaxies in Indus include the spiral NGC 7090 and the elliptical NGC 7049:
Hubble Sees NGC 7090- An actively star-forming galaxy
This image portrays a beautiful view of the galaxy NGC 7090, as seen by the NASA/ESA Hubble Space Telescope. The galaxy is viewed edge-on from the Earth, meaning we cannot easily see the spiral arms, which are full of young, hot stars.
However, a side-on view shows the galaxy’s disc and the bulging central core, where typically a large group of cool old stars are packed in a compact, spheroidal region. In addition, there are two interesting features present in the image that are worth mentioning.
First, we are able to distinguish an intricate pattern of pinkish red regions over the whole galaxy. This indicates the presence of clouds of hydrogen gas. These structures trace the location of ongoing star formation, visual confirmation of recent studies that classify NGC 7090 as an actively star-forming galaxy.
Second, we observe dust lanes, depicted as dark regions inside the disc of the galaxy. In NGC 7090, these regions are mostly located in lower half of the galaxy, showing an intricate filamentary structure. Looking from the outside in through the whole disc, the light emitted from the bright center of the galaxy is absorbed by the dust, silhouetting the dusty regions against the bright light in the background.
Dust in our galaxy, the Milky Way, has been one of the worst enemies of observational astronomers for decades. But this does not mean that these regions are only blind spots in the sky. At near-infrared wavelengths — slightly longer wavelengths than visible light — this dust is largely transparent and astronomers are able to study what is really behind it. At still longer wavelengths, the realm of radio astronomy, the dust itself can actually be observed, letting astronomers study the structure and properties of dust clouds and their relationship with star formation.
Lying in the southern constellation of Indus (The Indian), NGC 7090 is located about thirty million light-years from the Sun. Astronomer John Herschel first observed this galaxy on October 4, 1834.
The image was taken using the Wide Field Channel of the Advanced Camera for Surveys aboard the Hubble Space Telescope and combines orange light (colored blue here), infrared (colored red) and emissions from glowing hydrogen gas (also in red).
[https://www.nasa.gov/mission_pages/hubble/science/ngc7090.html]
Dramatically backlit dust in giant galaxy
A new Hubble image highlights striking swirling dust lanes and glittering globular clusters in oddball galaxy NGC 7049.
The NASA/ESA’s Hubble Space Telescope has captured this image of NGC 7049, a mysterious looking galaxy on the border between spiral and elliptical galaxies. NGC 7049 is found in the constellation of Indus, and is the brightest of a cluster of galaxies, a so-called Brightest Cluster Galaxy (BCG). Typical BCGs are some of the oldest and most massive galaxies. They provide excellent opportunities for astronomers to study the elusive globular clusters lurking within.
The globular clusters in NGC 7049 are seen as the sprinkling of small faint points of light in the galaxy’s halo. The halo – the ghostly region of diffuse light surrounding the galaxy – is composed of myriads of individual stars and provides a luminous background to the remarkable swirling ring of dust lanes surrounding NGC 7049’s core. Globular clusters are very dense and compact groupings of a few hundreds of thousands of stars bound together by gravity. They contain some of the first stars to be produced in a galaxy. NGC 7049 has far fewer such clusters than other similar giant galaxies in very big, rich groups. This indicates to astronomers how the surrounding environment influenced the formation of galaxy halos in the early Universe.
The image was taken by the Advanced Camera for Surveys on Hubble, which is optimized to hunt for galaxies and galaxy clusters in the remote and ancient Universe, at a time when our cosmos was very young.
[https://www.spacetelescope.org/news/heic0905/]
All Sky Automated Survey for SuperNovae (ASAS-SN) in 2015 detected a superluminous supernova, named ASASSN-15lh (also designated SN 2015L). Based on the study conducted by Subo Dong and team from the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University, ASAS-SN-15lh was two times more luminous than any supernova previously discovered, and at peak was almost 50 times more luminous than the entire Milky Way galaxy:
A candidate for the biggest boom yet seen (artistic illustration)
It is a candidate for the brightest and most powerful explosion ever seen- what is it? The flaring spot of light was found by the All Sky Automated Survey for Supernovae (ASASSN) in June of last year and labelled ASASSN-15lh. Located about three billion light years distant, the source appears tremendously bright for anything so far away: roughly 200 times brighter than an average supernova, and temporarily 20 times brighter than all of the stars in our Milky Way Galaxy combined. Were light emitted by ASASSN-15lh at this rate in all directions at once, it would be the most powerful explosion yet recorded. No known stellar object was thought to create an explosion this powerful, although pushing the theoretical limits for the spin-down of highly-magnetized neutron star- a magnetar- gets close. Assuming the flare fades as expected later this year, astronomers are planning to use telescopes including Hubble to zoom in on the region to gain more clues. The above-featured artist's illustration depicts a hypothetical night sky of a planet located across the host galaxy from the outburst.
[https://apod.nasa.gov/apod/ap160126.html]
[https://en.wikipedia.org/wiki/Indus_%28constellation%29]
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