Telescopium

What is Telescopium?

Constellations· Southern winter · a faint patch south of Sagittarius. Lacaille's tribute to the telescope. With one third-magnitude star and little else, it is remembered for its name rather than its shape; find it beneath Sagittarius in the southern winter sky.

Where Telescopium is in your sky right now: https://nowsky.org/solar/sky?sel=con:Telescopium — location and time set automatically, no login.

Stars of the figure

The 1 brightest of the 2 stars used in the figure (1 lines). Lower magnitude means brighter.

Constellation basics

Figures are representative approximations. Source: compiled from NASA and IAU public data.

Frequently asked

When can I see Telescopium?

Jul–Aug evenings; not visible from Korea.

How do I find Telescopium?

just south of Corona Australis, east of Ara.

What is the brightest star in Telescopium?

Alpha Telescopii, magnitude 3.5.

Where is Telescopium in the sky right now?

Open the sky view for your location and time and it shows the position in the sky right now.

The star said to hold the nearest black hole — a conclusion reversed in two years

In May 2020 it was announced that HR 6819, a 5th-magnitude star in Telescopium, harboured a black hole of four solar masses. At 1,000 light-years it would have been the nearest black hole known, beside a star visible to the naked eye, and it made headlines. The evidence was that one of two stars appeared to orbit something unseen every 40 days.

In 2022 another team reanalysed the same data and resolved the two stars directly with the VLT interferometer, concluding that there was no black hole, only a light star that had just been stripped of its mass and a fast-spinning star that had received it. The original team accepted the result. In the constellation Lacaille made to honour the telescope, the precision of a telescope corrected an earlier conclusion.

The constellation in depth

Telescopium is one of the fourteen constellations Lacaille introduced in the 1750s while charting the southern sky from the Cape of Good Hope; it honours the long refracting telescope, the emblem of science in his day. Originally drawn much larger, it was trimmed by later cartographers where it overlapped its neighbours, leaving a small, faint quadrilateral.

Alpha Telescopii, its brightest star at magnitude 3.5, is a blue-white subgiant about five times the Sun's mass. The constellation has few showpiece clusters or nebulae, though delta Telescopii is an optical double you can split in binoculars and the globular cluster NGC 6584 is a modest telescopic target. Most of what it offers rewards a telescope rather than the naked eye, which suits its name.

At declinations of −45° to −57° it never rises from Korea. In the southern hemisphere it climbs high on July and August evenings, south of the Sagittarius Teapot and below Corona Australis. In the Sky view, set Sydney as your location on an August evening. Switch on the constellation lines, since few of its stars stand out on their own.

Related

Figures are representative approximations. Simulated positions use J2000 mean elements.