Six Chandra X-ray composite images: a starburst galaxy, a galaxy cluster, a supernova remnant ring, Eta Carinae, the Cartwheel galaxy and the Helix nebula
The Universe in X-rays. Credit: Chandra X-ray Center (NASA/CXC)

Human consciousness, and with it knowledge, is perhaps the greatest privilege a living being can experience across the infinite distances and time of the Universe. Thus, to understand our surroundings on a universal scale is the greatest privilege of my life: a mind open beyond social and human superficialities.

Juan Facundo Albacete Colombo

Ph.D. in Astronomy · High-energy astrophysicist
CONICET researcher · Professor at the Universidad Nacional de Río Negro
Viedma (8500), Argentina

Juan Facundo Albacete Colombo beside a frozen lake in a snow-covered mountain landscape
Snow and still water in the Patagonian Andes

I study young massive star clusters and star-forming regions with X-ray telescopes, chiefly Chandra and XMM-Newton. My work centres on the hot plasma, massive stars and low-mass populations of Cygnus OB2 and Westerlund 1, and on statistical methods for low-count X-ray spectra. I am based at the Universidad Nacional de Río Negro, Sede Atlántica, in Viedma, Patagonia.

Active · since 2021

EWOCS: Westerlund 1 and 2

Member of the Extended Westerlund One and Two Chandra (and JWST) Survey, led from INAF – Palermo. The survey studies the X-ray population, Wolf–Rayet stars and diffuse emission of the most massive young cluster in the Milky Way.

  • Chandra/ACIS 1 Ms
  • JWST
  • Super star clusters
Active · Cygnus OB2 Legacy

Diffuse X-ray emission in Cygnus OB2

Mapping the hot gas that fills the Cygnus OB2 association and separating it from unresolved stars, using the Chandra Cygnus OB2 Legacy Survey.

  • Chandra/ACIS-I
  • Hot ISM
  • Massive star feedback
Active · since 2013

Spectral uncertainties at low photon counts

Statistical characterisation of how reliable X-ray spectral parameters are when sources yield only tens of photons, calibrated on simulated Chandra ACIS-I spectra.

  • Simulations
  • Spectral fitting
  • Statistics
Active · 2024–2029

OCEANS

External researcher in Overcoming Challenges in the Evolution and Nature of Massive Stars, a Horizon Europe project funded by the European Union.

  • Massive stars
  • Horizon Europe
Active · since 2015

ATHENA star formation group

Coordinator of the star formation working group in the community of ESA's Advanced Telescope for High Energy Astrophysics.

  • ESA
  • Future missions
Active · since 1999

MEGA-X campaign in the Carina Nebula

International ground- and satellite-based monitoring of the X-ray emitting massive stars of the Carina Nebula (X-MEGA). Optical spectroscopy of its targets revealed new massive O-type binaries and their orbits, and long-term monitoring followed the periodic events of η Carinae.

  • Optical spectroscopy
  • Massive binaries
  • η Carinae

Seven of my papers, each told through one of its figures. X-ray telescopes see the Universe at its hottest: gas at millions of degrees, stellar flares and the shock waves of exploded stars. The colours in these images are not what the eye would see; they encode the energy of the X-ray photons.

Colour-coded Chandra X-ray image of Westerlund 1: a diffuse glow of red, green and blue around a dense cluster of point-like stars
Westerlund 1 in X-rays. Red, green and blue show soft, medium and hard X-rays; the blue dot at lower left is a magnetar.

2026 · Astronomy & Astrophysics · First author

The hot breath of a super star cluster

EWOCS-VII: Unveiling the faint diffuse X-ray emission in Westerlund 1

Westerlund 1 is the closest super star cluster to the Sun, home to more than 100,000 stars. Its most massive stars blow winds so powerful that, when they collide, they heat the gas between the stars to tens of millions of degrees. After carefully removing almost five thousand individual stars from the deep Chandra images of the EWOCS survey, we could map this faint glow for the first time. In the core it comes from colliding winds of Wolf–Rayet stars; further out, the hot gas touches cold clouds and exchanges electrons with them.

Chandra observations
36
Stars removed
4,922
Gas temperature
21–48 MK
Read the paper · A&A 713, A79
Mosaic of Chandra X-ray images of Cygnus OB2 showing extended red, orange and blue diffuse emission
Diffuse X-ray map of Cygnus OB2, about 1.3 × 1.3 degrees. Soft emission in red, medium in green, hard in blue.

2023 · ApJ Supplement · First author

A stellar nursery wrapped in million-degree gas

Diffuse X-ray emission in the Cygnus OB2 association

Cygnus OB2 is one of the largest groups of massive stars in our Galaxy. Using 40 Chandra pointings that cover an area five times the full Moon, we removed nearly eight thousand stars to reveal the gas between them. That gas fills the whole region, heated by stellar winds that crash into each other and into the surrounding clouds. We also found the first signs of X-ray halos around some evolved massive stars.

Chandra pointings
40
Stars removed
7,924
X-ray power
4×10³⁴ erg/s
Read the paper · ApJS 269, 14
Colour map of temperature uncertainty as a function of absorption and plasma temperature, with contour lines
Uncertainty map for the measured temperature of a faint source with 90–100 photons. Dark blue means a precise answer; white means a poorly constrained one.

2023 · ApJ Supplement · First author

How much can a handful of photons tell us?

The statistical uncertainties on X-ray flux and spectral parameters from Chandra ACIS-I observations of faint sources

Most young stars in a distant cluster send us only a few dozen X-ray photons during an observation. How well can we measure their temperature or brightness from so little light? We simulated 150,000 artificial spectra to find out, and built maps that give the error bars directly. They let astronomers know how far they can trust a measurement before they even fit the data.

Simulated spectra
150,000
Photons per source
10–350
Tested on
Cygnus OB2
Read the paper · ApJS 269, 11
Two XMM-Newton colour images of the supernova remnant G296.8-0.3 with radio contours overlaid
G296.8-0.3 seen by XMM-Newton (colours) with the radio shell from the MOST telescope (white contours).

2012 · Astrophysics and Space Science · Co-author

The glowing remains of an exploded star

A multiwavelength study of the supernova remnant G296.8-0.3

When a massive star explodes, its shock wave heats the surrounding gas for thousands of years. Combining X-ray, radio and infrared images, we showed that this remnant lies at least 29,000 light-years away and contains gas at about 10 million degrees. Near its centre we found a point-like X-ray source that may be the neutron star left behind by the explosion.

Distance
> 9 kpc
Gas temperature
≈ 10 MK
Telescope
XMM-Newton
Read the paper · Ap&SS 337, 573
Chandra X-ray sources overlaid on a grey optical H-alpha image of the Carina Nebula, with a V-shaped dust lane outlined
X-ray stars of Trumpler 16 over an optical image of the Carina Nebula. Few sources appear behind the dark V-shaped dust lane.

2008 · Astronomy & Astrophysics · First author

A thousand young suns in the Carina Nebula

An X-ray survey of low-mass stars in Trumpler 16 with Chandra

Young stars like the early Sun are much brighter in X-rays than they are today, so X-ray images find them even inside dusty nebulae. In Trumpler 16, a 3-million-year-old cluster next to the giant star η Carinae, we detected over a thousand X-ray sources. Many of their planet-forming disks have survived the harsh light of their massive neighbours.

X-ray sources
1,035
Likely members
660
Stars with disks
~15%
Read the paper · A&A 490, 1055
Light curve of a young star showing a sudden rise in X-ray luminosity followed by an exponential decay
An X-ray flare from a young star in Cygnus OB2: a sudden rise, then a decay over a few hours. The shaded area is the energy released.

2007 · Astronomy & Astrophysics · First author

Stellar storms in young stars

X-ray flaring from the young stars in Cygnus OB2

Young stars are magnetically violent: their flares are far more powerful than those of today's Sun. We catalogued the flares of about a thousand young stars in Cygnus OB2 and compared them with stars in the Orion Nebula. Stars of 1 and 2 million years flare in the same way, which tells us this activity changes slowly in a star's youth.

Flares in Cygnus OB2
147
Flares in Orion
954
Flare duration
0.5–10 h
Read the paper · A&A 474, 495
XMM-Newton colour X-ray image of the Carina Nebula with the very bright source eta Carinae at the centre
The Carina Nebula seen by XMM-Newton. The brilliant source at the centre is η Carinae. Red, green and blue show low, medium and high energies.

2003 · Monthly Notices of the RAS · First author

The Carina Nebula through X-ray eyes

XMM-Newton X-ray observations of the Carina nebula

The Carina Nebula hosts some of the most massive stars known, including η Carinae. Using the European XMM-Newton satellite, we catalogued its X-ray sources and measured how the X-ray brightness of massive stars follows their total light. Some stars turned out to be surprisingly bright at high energies, a sign of colliding winds in binary systems.

X-ray sources
80
Monitoring time
~50 h
Energy range
0.3–12 keV
Read the paper · MNRAS 346, 704