A black hole masquerading as a star

Black holes are some of the most enigmatic objects in the universe. First conceptualized by the German-born theoretical physicist Albert Einstein (1879-1955) in his theory of general relativity, black holes have only recently been photographed.  

While it is impossible to optically image a black hole itself, the bright band of light referred to as the “accretion disk” swirling around a black hole can be photographed, as it was in 2019, when the first image of the massive black hole at the center of the M87 galaxy was captured.  

Very little is known about the origin and nature of black holes, other than that they are objects having such immense density and gravity that not even light can escape from them; the “black” refers to the absence of light coming from them. It is theorized that black holes exist in a multitude of sizes, ranging from small enough to pass through any object in the universe, to such massive objects as Phoenix A, a black hole having billions of solar masses located in the constellation of Phoenix. 

In 2023, the James Webb Space Telescope (JWST) imaged an intriguing object located billions of light-years from Earth in a low-mass dwarf galaxy in the constellation of Cetus – the Sea Monster. As this newly discovered object defied all known cosmic categories, it was labelled as a “black hole star,” an object that resembles both a black hole and a star.   

It was discovered during the JWST “Mirage or Miracle” (MoM) survey of galaxies in the early universe. Consequently, it was named MoM-BH*-1 (“black hole star – one”).  The object is believed to have formed approximately 660 million years after the Big Bang, when the core of a supermassive protostar collapsed into a stellar-mass black hole.  

Astronomers uncover an extraordinarily unusual cosmic object 

MoM-BH*-1 (MoM-1) first appeared as a bright red source of light in the JWST images. It had an extremely unusual colour profile, in that it was nearly invisible when viewed through blue filters, but highly visible when viewed through red filters; it was, in fact, one of the reddest distant objects ever recorded. Spectroscopic analysis of MoM-1 indicates that it contains the strongest Balmer break of any known astronomical objects measured in redshift.  

A Balmer break, also known as a Balmer jump, is the difference in the intensity of the stellar spectrum on either side of the limit of the Balmer series of hydrogen – one of a set of six named series respecting the spectral line emissions of the hydrogen atom. The strong Balmer break of MoM-1 indicates the presence of very dense hydrogen gas. 

An analysis of MoM-1’s chemical composition found vast amounts of hydrogen and helium, but no evidence of metals or heavier elements; this discovery excludes ordinary stars as the object’s light source. Also, although its spectrum links it to hydrogen absorption, MoM-1’s Balmer break far exceeds what normal stars or normal star populations typically produce; even the reddest stellar populations discovered to date show a Balmer break less than one-third that of MoM-1. Its broad emission lines combined with deep absorption features indicate that MoM-1 exists in an environment of unusually dense gas.  

At first, astronomers thought they might have found a new type of stellar atmosphere, as MoM-1’s brightness exceeded that which a stellar body of that scale could generate from nuclear fusion. To understand MoM-1 formation, astronomers developed a computer model in which MoM-1 contained a massive black hole surrounded by a dense cocoon of gas, giving MoM-1 the appearance of a huge star-like object.  

The model demonstrated that the dense envelope of hydrogen would absorb and scatter the object’s radiation, thereby producing its unusual red shift colour and distinctive spectral pattern. The black hole’s immense radiation would also be strong enough to be able to pass through the dense cloud of gas, and to be detected by the JWST. 

MoM-1 may be related to unexplained ‘little red dots’

Astronomers also discovered evidence that MoM-1 may have increased in brightness by approximately 30 per cent over a two-month period, behaviour typical of massive black holes rapidly feeding on surrounding material, confirming their theory that MoM-1 was, in fact, a black hole masquerading as a star.  

There is a theory that the MoM-1 object might possibly be related to a yet-as-unexplained group of astronomical sources referred to as “little red dots”. Little red dots are mysterious red sources of light found in photographs of the early universe that are believed to be black holes surrounded by dense ionized gas. Interestingly, these little red dots do not appear in astro-photographs from more recent cosmic periods. 

Whatever their origin, little red dots and black hole stars such as MoM-1 are proof that the universe is still quite capable of demonstrating how very little we know and, more importantly, understand the universe in which we dwell. No doubt, there are many more astronomical mysteries such as MoM-1 waiting to be discovered.  

This week’s sky 

Mercury (mag. -1.4, in Cancer – the Crab) will pass behind the sun (superior solar conjunction) on Aug. 27 and therefore will not be observable this coming week. On Aug. 27, Mercury will begin its passage around the far side of the sun, referred to as superior solar conjunction. 

Venus (mag. -4.4, in Virgo – the Maiden) becomes visible around 8:25 p.m. ADT, 8 degrees above the southwest horizon as dusk gives way to darkness, before sinking towards the horizon and setting about 9:25 p.m. ADT.  

Mars (mag. +1.3, in Gemini – the Twins) rises in the eastern, predawn sky around 1:45 a.m. ADT, reaching 36 degrees above the eastern horizon, before fading from view by about 5:30 a.m. ADT.  

Jupiter (mag. -1.8, in Cancer) rises around 4:35 a.m. ADT, reaching 12 degrees above the eastern horizon, before fading from view by about 6 a.m. ADT. 

Saturn (mag. +0.4, in Pisces – the Fish) becomes accessible 10 degrees above the eastern horizon around 10:45 p.m. ADT, reaching its highest point in the sky 46 degrees above the southern horizon shortly before 4 a.m. ADT, before being lost to the dawn twilight 40 degrees above the southwest horizon around 5:45 a.m. ADT. Saturn and the Moon will make an apparent close approach (an appulse) with one another, as viewed from Earth, at 11:32 p.m. ADT on Aug. 30. 

Uranus (mag. +5.7, in Taurus – the Bull) rises around 11:35 p.m. ADT, reaching 52 degrees above the southeast horizon, before fading from view in the dawn twilight by about 5 a.m. ADT. 

Neptune (mag. +7.8 in Pisces), now approaching opposition, becomes accessible 21 degrees above the southeast horizon by about 11:30 p.m. ADT, before reaching its highest point in the sky 43 degrees above the southern horizon around 3:15 a.m. ADT, and then disappearing into the dawn twilight around 5 a.m. ADT, 38 degrees above the southwest horizon.  

Partial lunar eclipse coming 

On Aug. 27, there will be a partial lunar eclipse. It will begin at 10:25 p.m. ADT, and finish at 4:02 a.m. ADT on the Aug. 28. A maximum eclipse will occur at 1:14 a.m. ADT, with 93 per cent of the lunar surface covered by the Earth’s shadow. August’s Full Moon at 1:18 a.m. ADT on the Aug. 28 is often referred to as the “Sturgeon Moon,” in reference to the time of the year when sturgeon, North America’s largest fish, run up the rivers of the Great Lakes. 

Errata: I mixed up my distance figures in last week’s article. One astronomical unit (AU) is equal to 148,800,000 kilometres (not 93,000,000). As a consequence, Jupiter orbits the sun at an average distance of 774,206,400 km or 5.203 AU. My apologies. Thanks to my sharp-eyed readers who caught the error. 

Until next week, clear skies. 

Events: 

Aug. 25 – Moon at aphelion (farthest point from the sun); 5:21 p.m. ADT; 150,749,280 km or 1.0131 AU 

Aug. 27 – Mercury at superior solar conjunction at 2:11 p.m. ADT; partial lunar eclipse starts at 10:25 p.m. ADT (see above) 

Aug. 28 – Partial lunar eclipse maximum at 1:14 a.m. ADT; full “Sturgeon Moon” at 1:18 a.m. ADT 

Aug. 30 – Close approach of the moon and Saturn at 11:32 p.m. ADT